It'll definitely Catch Fish as long it's about The Same Size as The Fish are Feeding on.
I find Synthetic Wool Can be substituted & used as Dubbing It's Cheaper & there are many colours available you just might have to occassionally add a little Floatant to keep it afloat Longer.
Brian.

Looks like an Slate Drake (Isonychia) to me as well -- unless you have very small thumbnails ;-).

There seems to be some controversy and / or regional variation in this, but I believe that most Isos hatch by crawling out of the water. Iso nymphs are very good swimmers and I've generally done much better with a nymph than dun during a Iso hatch.

So I'd make sure you have some Iso nymphs as well. A large hare's ear will work, but that are lots of patterns out there.